Laser beam phase-modulation device, laser beam steering device and laser beam steering system including the same

ABSTRACT

A laser beam phase-modulation device, a laser beam steering device, and a laser beam steering system including the same are provided. The laser beam phase-modulation device includes a refractive index conversion layer having a refractive index that is changed according to an electrical signal applied thereto, the refractive index conversion layer including an upper surface on which the laser beam is incident and a lower surface opposite the upper surface, at least one antenna pattern embedded in the upper surface of the refractive index conversion layer, and a metal mirror layer provided under the lower surface of the refractive index conversion layer and configured to reflect the laser beam.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/670,509, filed on Aug. 7, 2017, which claims priority from KoreanPatent Application No. 10-2016-0152234, filed on Nov. 15, 2016, in theKorean Intellectual Property Office, the disclosures of which areincorporated herein in their entirety by reference.

BACKGROUND 1. Field

Apparatuses and methods consistent with example embodiments relate to alaser beam phase-modulation device, a laser beam steering device, and alaser beam steering system including the same.

2. Description of the Related Art

In order to steer a beam such as a laser to a desired position, a methodof mechanically rotating a laser-irradiated portion has been used, aswell as a method of using an interference of a laser beam bundle fromseveral pixels or waveguides by using an Optical Phased Array (OPA)method. In the OPA method, a laser beam may be steered by electricallyor thermally controlling unit cells or waveguides.

In order to mechanically drive a laser beam, a motor or amicro-electro-mechanical system (MEMS) structure must be applied.However, in this case, the volume of the entire device becomes large,and the cost of parts may increase. In addition, noise may occur when amotor is applied, and application of the MEMS structure to various partsmay be limited due to vibrations and the like.

SUMMARY

Example embodiments provide a laser beam phase-modulation device, alaser beam steering device, and a laser beam steering system includingthe same.

According to an aspect of an example embodiment, there is provided adevice configured to modulate a phase of a laser beam, the deviceincluding: a refractive index conversion layer having a refractive indexthat changes according to an electrical signal applied thereto, therefractive index conversion layer including an upper surface on whichthe laser beam is incident and a lower surface opposite the uppersurface; at least one antenna pattern embedded in the upper surface ofthe refractive index conversion layer; and a metal mirror layer providedunder the lower surface of the refractive index conversion layer andconfigured to reflect the laser beam.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side surfaces and the lower surface of the atleast one antenna pattern.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side, lower, and upper surfaces of the at leastone antenna pattern.

The device may further include an insulating layer provided between theupper surface of the refractive index conversion layer and the at leastone antenna pattern.

The insulating layer may include at least one of silicon dioxide (SiO₂),silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), hafnium dioxide (HfO₂),hafnium silicon dioxide (HfSiO₂), and zirconium dioxide (ZrO₂).

The refractive index conversion layer may include an oxidesemiconductor.

The oxide semiconductor may include at least one of Indium-Tin-Oxide(ITO), Indium-Zinc-Oxide (IZO), Ga—In—Zn-Oxide (GIZO), Al—Zn-Oxide(AZO), Ga—Zn-Oxide (GZO), and ZnO.

The at least one antenna pattern may include at least one of silver(Ag), gold (Au), aluminum (Al), platinum (Pt), titanium nitride (TiN),and tantalum nitride (TaN).

According to an aspect of another example embodiment, there is provideda device configured to steer a laser beam, the device including: aplurality of unit cells, each of the unit cells including: a refractiveindex conversion layer having a refractive index that changes accordingto an electrical signal applied thereto, the refractive index conversionlayer including an upper surface on which the laser beam is incident anda lower surface opposite the upper surface; at least one antenna patternembedded in the upper surface of the refractive index conversion layer;a metal mirror layer provided under the lower surface of the refractiveindex conversion layer and configured to reflect the laser beam; and aunit cell driver configured to apply the electrical signal to therefractive index conversion layer.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side surfaces and the lower surface of the atleast one antenna pattern.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side, bottom, and upper surfaces of the at leastone antenna pattern.

The plurality of unit cells may be arranged two-dimensionally.

The plurality of unit cells may be configured to steer the laser beam byforming a refractive index profile that changes with time.

The device may further include an insulating layer provided between therefractive index conversion layer and the at least one antenna pattern.

According to an aspect of another example embodiment, there is provideda laser beam steering system including: a laser light source configuredto emit a laser beam; a laser beam steering device configured to steerthe laser beam incident from the laser light source; and a detectorconfigured to detect the steered laser beam, wherein the laser beamsteering device includes: a plurality of unit cells, each of the unitcells including: a refractive index conversion layer having a refractiveindex that changes according to an electrical signal applied thereto,the refractive index conversion layer including an upper surface onwhich the laser beam is incident and a lower surface opposite the uppersurface; at least one antenna pattern embedded in the upper surface ofthe refractive index conversion layer; a metal mirror layer providedunder the lower surface of the refractive index conversion layer andconfigured to reflect the laser beam; and a unit cell driver configuredto apply the electrical signal to the refractive index conversion layer.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side surfaces and the lower surface of the atleast one antenna pattern.

The at least one antenna pattern may have an upper surface, a lowersurface, and side surfaces, and the refractive index conversion layermay be provided on the side, lower, and upper surfaces of the at leastone antenna pattern.

The plurality of unit cells may be arranged two-dimensionally.

The plurality of unit cells may be configured to steer the laser beam byforming a refractive index profile that changes with time.

The laser beam steering system may further include an insulating layerprovided between the refractive index conversion layer and the at leastone antenna pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of exemplary embodiments,taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a laser beam steering device;

FIG. 2 is a perspective view of a laser beam steering device accordingto an example embodiment;

FIG. 3 is a cross-sectional view of a unit cell of a laser beam steeringdevice according to an example embodiment;

FIG. 4 is a graph illustrating finite-difference time-domain (FDTD)simulation results of a phase according to an applied voltage in ageneral laser beam steering device A and a laser beam steering device Baccording to an example embodiment;

FIG. 5 is a cross-sectional view of a laser beam steering deviceaccording to another example embodiment; and

FIG. 6 is a view of a laser beam steering system according to anotherexample embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentexample embodiments may have different forms and should not be construedas being limited to the descriptions set forth herein. Accordingly, theexample embodiments are described below, by referring to the figures, toexplain aspects. Expressions such as “at least one of,” when preceding alist of elements, modify the entire list of elements and do not modifythe individual elements of the list.

Throughout the specification, it will be understood that when a unit isreferred to as being “connected” to another element, the unit may be“directly connected” to the other element or “electrically connected” tothe other element in a state in which intervening elements are present.

FIG. 1 is a cross-sectional view of a general laser beam steering device10.

Referring to FIG. 1, a plurality of antenna patterns 21 are providedover an upper portion of a refractive index conversion layer 17 having arefractive index that is converted by an electrical signal. A metalmirror layer 13 is provided under the refractive index conversion layer17 and a unit cell driver 11 is provided under the metal mirror layer13. An insulating layer 19 is provided between the refractive indexconversion layer 17 and the antenna patterns 21. In such a structure,when a voltage is applied to the refractive index conversion layer 17 bythe unit cell driver 11, a carrier density of the refractive indexconversion layer 17 changes, and thus, a refractive index is changed.

FIG. 2 is a perspective view of a laser beam steering device 100according to an example embodiment.

Referring to FIG. 2, the laser beam steering device 100 may include aplurality of unit cells P arranged in a two-dimensional (2D) form. Eachof the unit cells P has a predetermined refractive index, so that theunit cells P may form a refractive index profile. The plurality of unitcells P may form a refractive index profile that changes with time,thereby steering a laser beam incident on the laser beam steering device100 in a desired direction.

FIG. 3 is a cross-sectional view of a unit cell P of the laser beamsteering device 100 according to an example embodiment.

Referring to FIG. 3, the unit cell P of the laser beam steering device100 may include a refractive index conversion layer 130, a plurality ofantenna patterns 150 embedded in the refractive index conversion layer130, a metal mirror layer 120 provided under the refractive indexconversion layer 130, and a unit cell driver 110 for applying anelectrical signal to the refractive index conversion layer 130.

A carrier density of the refractive index conversion layer 130 maychange depending on the application of an electrical signal (e.g., avoltage) thereto. The change of the carrier density may change arefractive index of the refractive index conversion layer 130, and thelaser beam may be steered according to the change of the refractiveindex.

The refractive index conversion layer 130 may include a material inwhich a carrier density thereof varies with a voltage applied thereto.For example, the refractive index conversion layer 130 may include anoxide semiconductor. As a specific example, the refractive indexconversion layer 130 may include a transparent conductive oxide (TCO).The TCO may be, for example, Indium-Tin-Oxide (ITO), Indium-Zinc-Oxide(IZO), Ga—In—Zn-Oxide (GIZO), Al—Zn-Oxide (AZO), or Ga—Zn-Oxide (ZnO),but embodiments are not limited thereto.

In general, since refractive index conversion efficiency improves as acarrier density is increased, the refractive index conversion layer 130may include a material having a high carrier density. As such, when therefractive index conversion layer 130 has a high carrier density, themaximum phase of a laser beam may increase as the refractive indexconversion efficiency is improved.

The refractive index conversion layer 130 may be formed to be relativelythin so as not to affect a wavelength of a laser beam incident thereon.For example, the refractive index conversion layer 130 may have athickness of about 5 nm or less. However, the refractive indexconversion layer 130 is not limited thereto, and the refractive indexconversion layer 130 may have various thicknesses.

The plurality of antenna patterns 150 are embedded in the refractiveindex conversion layer 130. For example, the refractive index conversionlayer 130 may be provided on side surfaces and a bottom surface of eachof the plurality of antenna patterns 150. Alternatively, the refractiveindex conversion layer 130 may be provided on at least two sides of eachof the plurality of antenna patterns 150. FIG. 3 shows an example inwhich four antenna patterns are provided corresponding to one unit cellP, as an example. However, embodiments are not limited thereto, and theplurality of antenna patterns 150 may be provided corresponding to oneunit cell P.

The plurality of antenna patterns 150 may be provided to form ametasurface for beam steering. Here, the antenna patterns 150 mayinclude, for example, a metal or an alloy including at least one ofsilver (Ag), gold (Au), aluminum (Al), and platinum (Pt). In addition,the antenna patterns 150 may include a metal nitride such as titaniumnitride (TiN) or tantalum nitride (TaN). However, the above-mentionedmaterials are merely examples, and the antenna patterns 150 may includevarious materials.

FIG. 2 shows an example in which the antenna patterns 150 have arectangular shape in which the antenna patterns 150 are arranged atregular intervals. However, embodiments are not limited thereto, and theantenna patterns 150 may have various shapes. For example, the antennapatterns 150 may have a polygonal shape including a circle, an ellipse,a triangle, or a square. In addition, the antenna patterns 150 may haveirregular shapes.

A distance between the antenna patterns 150 may be less than, forexample, ½ or ⅓ of a wavelength of a laser beam incident thereon. Forexample, when the wavelength of the laser beam incident thereon is 1500nm, an interval between the antenna patterns 150 may be 500 nm or less.However, embodiments are not limited thereto. Furthermore, although theantenna patterns 150 may be arranged at regular intervals, embodimentsare not limited thereto. The antenna patterns 150 may be arranged atirregular intervals.

An insulating layer 140 may be provided between the refractive indexconversion layer 130 and the antenna patterns 150. The insulating layer140 may include various kinds of insulating materials. For example, theinsulating layer 140 may include an insulating material havingresistance of at least 1 MΩ. As a specific example, the insulating layer140 may include, but is not limited to including, silicon oxide, siliconnitride, aluminum oxide (Al₂O₃), zinc oxide (ZrO₂), or hafnium oxide(HfO₂).

The metal mirror layer 120 may be provided on a lower surface of therefractive index conversion layer 130. The metal mirror layer 120 may beprovided to improve light efficiency of the laser beam steering device100 by reflecting a laser beam incident thereon. The metal mirror layer120 may include, for example, a same metal material as that of theantenna patterns 150. As a specific example, the metal mirror layer 120may include at least one of Ag, Au, Al, and Pt. However, embodiments arenot limited thereto, and the metal mirror layer 120 may include a metalmaterial different from that of the antenna patterns 150.

The metal mirror layer 120 may also function as an electrode forapplying a voltage to the refractive index conversion layer 130. Forexample, when a voltage is applied between the metal mirror layer 120and the antenna patterns 150 by the unit cell driver 110, a carrierdensity of the refractive index conversion layer 130 changes, andtherefore, a refractive index of the light guide plate 130 may bechanged.

The unit cell driver 110 may apply an electrical signal, such as avoltage, to the refractive index conversion layer 130. The unit celldriver 110 may be provided under the metal mirror layer 120. The unitcell driver 110 includes, for example, one transistor and one capacitorto apply a voltage to the refractive index conversion layer 130 in theunit cell P. The unit cell driver 110 may apply a voltage between theantenna patterns 150 and the metal mirror layer 120 or may apply avoltage between the antenna patterns 150 and the refractive indexconversion layer 130.

The plurality of unit cells P are independently driven by correspondingunit cell drivers 110, thereby exhibiting different refractive indexes,and thus a refractive index profile of the plurality of unit cells P maybe formed. Since the refractive index profile may be changed by changinga voltage applied to the unit cells P, the laser beam may be steered ina desired direction.

The laser beam steering device 100 having the above structure may ensurea maximum phase change even at a low driving voltage by configuring theantenna patterns 150 to be embedded in the refractive index conversionlayer 130, and thus, stability of the steering device 100 may beimproved.

FIG. 4 is a graph illustrating finite-difference time-domain (FDTD)simulation results of a phase according to an applied voltage in ageneral laser beam steering device A and a laser beam steering device Baccording to an exemplary embodiment. In FIG. 4, the general laser beamsteering device A has the sectional structure of FIG. 1, and the laserbeam steering device B according to the exemplary embodiment has thesectional structure of FIG. 3. ITO is used for the refractive indexconversion layer 17 in the general laser beam steering device A and alsoused for the refractive index conversion layer 130 in the laser beamsteering device B according to an example embodiment.

Referring to FIG. 4, the laser beam steering device B according to anexample embodiment applies a voltage of about 2V to obtain a phasechange of about 200 degrees, and the general laser beam steering deviceA applies a voltage of about 3V to obtain a phase change of about 200degrees. That is, it can be seen that the laser beam steering device Baccording to an example embodiment may secure a high phase change with alow applied voltage as compared with the general laser beam steeringdevice A. Therefore, the laser beam steering device B according to anexample embodiment may realize a high phase change even at a low drivingvoltage, and the low driving voltage may improve stability of the laserbeam steering device B.

FIG. 5 is a cross-sectional view of a laser beam steering device 200according to another example embodiment. FIG. 5 shows one unit cellamong a plurality of unit cells constituting the laser beam steeringdevice 200.

Referring to FIG. 5, a unit cell of the laser beam steering device 200includes refractive index conversion layers 230 a and 230 b in whichcarrier densities thereof vary according to an electrical signal, aplurality of antenna patterns 250 embedded in the refractive indexconversion layers 230 a and 230 b, a metal mirror layer 220 providedunder the refractive index conversion layer 230 a, and a unit celldriver 210 for applying an electrical signal to the refractive indexconversion layers 230 a and 230 b. Furthermore, an insulating layer 240may be provided between the refractive index conversion layers 230 a and230 b and the antenna patterns 250.

The refractive index conversion layers 230 a and 230 b may include amaterial in which a carrier density thereof varies with a voltageapplied thereto. For example, the refractive index conversion layers 230a and 230 b may include an oxide semiconductor such as a TCO or thelike. However, embodiments are not limited thereto. The refractive indexconversion layers 230 a and 230 b may be formed to have a relativelythin thickness of about 5 nm or less so as not to affect a wavelength ofa laser beam incident thereon.

The plurality of antenna patterns 250 are embedded in the refractiveindex conversion layers 230 a and 230 b. For example, the refractiveindex conversion layers 230 a and 230 b may be provided on left side,right side, lower, and upper surfaces of each of the plurality ofantenna patterns 250. Alternatively, the refractive index conversionlayers 230 a and 230 b may be provided on at least three sides of eachof the plurality of antenna patterns 250. The antenna patterns 250 mayinclude, for example, a metal or an alloy including at least one of Ag,Au, Al, and Pt. In addition, the antenna patterns 250 may include ametal nitride such as TiN or TaN. The distance between the antennapatterns 250 may be less than, for example, ½ or ⅓ of a wavelength of alaser beam incident thereon.

The insulating layer 240 may be provided between the refractive indexconversion layers 230 a and 230 b and the antenna patterns 250. Theinsulating layer 240 may include, for example, an insulating materialhaving resistance of at least 1 MO. As a specific example, theinsulating layer 240 may include, but is not limited to, silicon oxide,silicon nitride, Al₂O₃, ZrO₂, or HfO₂.

The metal mirror layer 220 may be provided on a lower surface of therefractive index conversion layer 230 a. For example, the metal mirrorlayer 220 may include, but is not limited to including, a same metalmaterial as that of the antenna patterns 250. The metal mirror layer 220may also function as an electrode for applying a voltage to therefractive index conversion layers 230 a and 230 b.

The unit cell driver 210 may apply an electrical signal, such as avoltage, to the refractive index conversion layers 230 a and 230 b. Theunit cell driver 210 may be provided under the metal mirror layer 220.The unit cell driver 210 may apply a voltage between the antennapatterns 250 and the metal mirror layer 220 or may apply a voltagebetween the metal mirror layer 220 and the refractive index conversionlayers 230 a and 230 b, thereby controlling a carrier density of theconversion layers 230 a and 230 b.

A maximum phase change even at a low driving voltage may be ensured inthe laser beam steering device 200 having the above structure due tohaving a configuration in which the antenna patterns 250 are embedded inthe refractive index conversion layers 230 a and 230 b, and thus,stability of the steering device 200 may be improved.

FIG. 6 is a view of a laser beam steering system 1000 according toanother example embodiment. FIG. 6 schematically illustrates the laserbeam steering system 1000 to which the laser beam steering deviceaccording to the example embodiments described above may be applied.

Referring to FIG. 6, the laser beam steering system 1000 according to anexample embodiment may include a laser light source 510 which emits alaser beam, a laser beam steering device 500 which steers the laserbeam, a detector 520 which detects the steered laser beam, and a driver530. The driver 530 may include a driving circuit for driving the laserlight source 510, the laser beam steering device 500, and the detector520.

For example, a laser diode may be used as the laser light source 510.However, this is merely an example and various other types of lightsources may be used. The laser beam emitted from the laser light source510 is incident on the laser beam steering device 500. The laser beamsteering device 500 steers the laser beam incident thereon to a desiredposition. The laser beam steering device 500 may include the laser beamsteering devices 100 and 200 according to the above-described exemplaryembodiments. In addition, when the laser beam steered by the laser beamsteering device 500 is irradiated to an object and is reflected, thedetector 520 may detect the reflected laser beam. The laser beamsteering system 1000 having the laser beam steering device 500 may havevarious applications, such as in a depth sensor, a 3D sensor, or lightdetection and ranging (LiDAR).

As described above, according to the example embodiments, an area of arefractive index conversion layer for driving antenna patterns may beincreased. In more detail, a laser beam steering device has a structurein which antenna patterns are embedded in a refractive index conversionlayer, so that when a laser beam incident on the antenna patterns isreflected, influence of the refractive index conversion layer on thelaser beam may increase. Also, the laser beam steering device accordingto the example embodiments may ensure a maximum phase change even at alow driving voltage, and the low driving voltage may improve stabilityof the laser beam steering device.

It should be understood that the example embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each embodimentshould typically be considered as available for other similar featuresor aspects in other embodiments.

While example embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. A device for modulating a phase of a laser beam,the device comprising: a refractive index conversion layer having arefractive index that changes according to an electrical signal appliedthereto, the refractive index conversion layer comprising an uppersurface on which the laser beam is incident and a lower surface oppositethe upper surface; at least one antenna pattern embedded in the uppersurface of the refractive index conversion layer; an insulating layerdisposed between the refractive index conversion layer and the at leastone antenna pattern; and a metal mirror layer provided under the lowersurface of the refractive index conversion layer and configured toreflect the laser beam; wherein the at least one antenna pattern has anupper surface, a lower surface, and side surfaces, wherein therefractive index conversion layer is provided on the side surfaces andthe lower surface of the at least one antenna pattern, wherein the atleast one antenna pattern has at least one of a metal, an alloy, and ametal nitride, and wherein the insulating layer is disposed to cover thelower surface, and the entire side surfaces of the at least one antennapattern.
 2. The device of claim 1, wherein the insulating layercomprises at least one of silicon dioxide (SiO2), silicon nitride(Si3N4), aluminum oxide (Al2O3), hafnium dioxide (HfO2), hafnium silicondioxide (HfSiO2), and zirconium dioxide (ZrO2).
 3. The device of claim1, wherein the refractive index conversion layer comprises an oxidesemiconductor.
 4. The device of claim 3, wherein the oxide semiconductorcomprises at least one of Indium-Tin-Oxide (ITO), Indium-Zinc-Oxide(IZO), Ga—In—Zn-Oxide (GIZO), Al—Zn-Oxide (AZO), Ga—Zn-Oxide (GZO), andZnO.
 5. The device of claim 1, wherein the at least one antenna patterncomprises at least one of silver (Ag), gold (Au), aluminum (Al),platinum (Pt), titanium nitride (TiN), and tantalum nitride (TaN).